The present invention relates to suspension struts and, more particularly, to suspension struts having damping.
Suspension struts may be employed to join a suspended mass with a suspending mass, for example, a vehicle body with vehicle wheels and/or other suspension components. For example, such suspension struts may be incorporated in mining vehicles and similar vehicles. The suspension struts of mining vehicles and the like may be subjected to large variations in load. More particularly, when a mining vehicle is empty, the suspension strut may bear only the relatively small load of the vehicle body. However, the full cargo load for which the vehicle is designed may exceed 80 tons. The suspension struts for such vehicles should be capable of sufficiently absorbing wheel travel or vibration for any load or displacement within the designed range of the vehicle in order to reduce or eliminate disruption of the vehicle or its cargo. It is particularly desirable to avoid bottoming out of the suspension strut in use. The suspension struts should also be durable, both in terms of fatigue resistance and resistance to damage from impacts, overloading and various environmental hazards.
It is also desirable to minimize rocking and oscillation of the mining vehicle or other suspended mass. To minimize these unsettling movements, damping of the suspension strut""s compression and/or extension may be required.
According to embodiments of the present invention, a suspension strut includes a housing assembly including first and second opposed housing members. The first and second housing members are relatively movable along an axis. At least the first housing member includes an engagement surface. At least one compressible spring member is interposed between the first and second housing members. The spring member includes a peripheral portion. The strut is configured such that, when the first and second housing members are relatively displaced along the axis in a prescribed direction, the spring member is axially compressed to provide a spring force opposing further relative displacement between the first and second housing members in the prescribed direction, and the peripheral portion frictionally engages the engagement surface over an area of engagement to provide dynamic damping between the first and second housing members.
Preferably, the area of engagement between the peripheral portion and the engagement surface increases with relative displacement between the first and second housing members in the prescribed direction and thereby increases the amount of the dynamic damping. Preferably, the housing assembly and the spring member are relatively arranged and configured such that deflection of the spring member responsive to axial compression is limited by the housing assembly.
The spring member may be formed of an elastomeric material. The spring member may be toroidally shaped. A plurality of the spring members may be provided in stacked relation. A separator plate may be interposed between at least two of the spring members.
The spring member may include a projection extending from an outer periphery of the spring member, the peripheral portion forming a part of the projection. The first housing member may include a tubular sleeve having an inner surface with the engagement surface forming a part of the inner surface.
The suspension strut may include a second tube forming a part of the second housing member and slidably received in the first tube, the second tube having a second engagement surface, and a second spring element disposed in the second tube and frictionally engaging the second engagement surface. A spacer may be interposed between the first spring element and the second spring element. This spacer may be axially displaceable relative to each of the first and second tubes. A bearing member may surround the second tube and be interposed between said first and second tubes.
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the Figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention.